Master cylinder puking fluid

Nope, no cheesy chrome covers for me. The cover came on the master cylinder when I got it. Brakes work MINT except for this one problem. It will puke the fluid out until the front chamber is completely empty, then I notice a drop in braking performance because the rears arn't doing their part anymore. Fill the resivoir up and drive it (without bleeding even, and before anyone says it, NO, that isn't the problem, I tried waisting my time and a lot of fluid rebleeding the brakes the first half dozen times or so.) and they will come right back, working just perfect except for the fluid spooging thing. I know plenty about brakes and this has me utterly baffled. I am going to try another master cyclinder though. Still under a warranty so it will only cost me the time to change it out and bleed them. Really really strange. :sad1: